The invention relates to a vacuum control system deployed in a vehicle to control the operation of selected devices such as an air conditioning system or throttle flap. More particularly, this invention relates to a temperature sensitive vacuum control system for controlling actuation of a selected device in response to the variance of the temperature of water or other fluid in a vehicle cooling system.
The November 1976 information pamphlet "Klixon Automotive Valves" distributed by Texas Instruments Holland B.V. makes known thermo-valves as control valves for the control of heating and air-conditioning equipment by means of a vacuum and as a function of the cooling-water temperature. Each thermo-valve consists of a screw-in portion provided with a temperature sensor and of a connector portion with connections for pressure lines. At a specific temperature, communication between the connections is either blocked or opened.
An object of the present invention is to provide a vacuum control system for devices in vehicles which works as precisely as possible and which includes thermo-valves that are activated according to a predetermined cooling-water temperature.
According to the present invention, an apparatus for controlling a selected device within a vehicle includes a vacuum source, a first thermo-valve, a device actuator, and a second thermo-valve. The preceding four elements are sequentially coupled for fluid communication by fluid conduits. The object is achieved due to the fact that the first thermo-valve precedes the device actuator and the second thermo-valve follows the device actuator in the control line. Further, the preceding first thermo-valve is closed and the following second thermo-valve is opened to the atmosphere whenever a selected threshold temperature of the water or other fluid in the vehicle cooling system is reached or surpassed.
The vacuum control of the present invention advantageously ensures direct transmission of control signals to the device actuator. Control of the device with a rapid and simple action is achieved as a result. Further, a vacuum control circuit is much simpler to design than the control circuits of an electrical control system.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.